Gamma plugin

Plugin BPP_Gamma allows to adjust gamma separately for each of RGB channels of picture. At first glance it may seem that gamma works similar to picture brightness. But it is not so. Lets feed the picture with gradient fill in three RGB channels from test signal generator. On the screenshot you may see that ADC characteristics of tuner is almost linear, it is proven by the linear diagram of level distribution on X axis.

Nevertheless, it may seem that dark tones prevail on the picture. Indeed, this may take place on translation of some, especially old, movies. It is natural desire to increase brightness of the picture in this case. This may be done by standard tuner settings.

Indeed the picture became more bright, but the black color disappeared and, which is the worst, bright tones became saturated that brought to loose of the picture details on saturated areas of picture. To prevent this, it is additional parameter provided to set – gamma. On gamma correction black areas of picture remain black, light remain light, and the mid-tones change in logarithmic law.

Plugin BPP_Gamma allows to set gamma separate for each of RGB channels of picture and individually for each TV channel.

In spite of the fact that gamma corrects RGB values, plugin works not only in RGB24 format, but in YUY2 also. But it requires additional CPU resources. Gamma correction in YUY2 format takes about 20% of CPU time (for a picture of size 768*576). In contrast, in RGB24 format the CPU load is only about 4-5%.